The Hemagglutination Inhibition Assay (HAI) was developed over 70 years ago as a means to measure influenza-specific antibody levels in serum. The HAI has since been applied to many other hemagglutinin-containing viruses such as rubella, measles, mumps, parainfluenza, adenoviruses, polyomaviruses and arboviruses, to name a few. Currently, the HAI is recognized as the so-called gold-standard serologic test for typing influenza antibodies in humans and animals and it is widely used in influenza surveillance and vaccine testing.
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